Reading the related RFCs there is no mention that filename="" is not allowed and the existence of the filename parameter should be enough to treat it as a file.
looking at django/http/multipartparser.py
165ff

file_name = disposition.get('filename')
if not file_name:
continue

this would need to set a default filename instead of bailing out
(i.e. if file_name == : file_name = 'data.bin)